Contamination detection has become increasingly significant, particularly with rapid evolution of high-tech industries. For example, semiconductor industry has developed technology for precisely producing microelectronic devices and integrated circuits. In order to reliably produce such products, highly stringent contamination standards must be maintained in production facilities of such products.
In an effort to control contamination during a production process, clean rooms are frequently used. A clean room is a room in which air filtration, air distribution, utilities, materials of construction, equipment, and other operating procedures are specified and regulated to control airborne particle concentrations to meet appropriate airborne particulate cleanliness classifications. Clean rooms are used extensively in semiconductor manufacturing, biotechnology, pharmaceutical, disk drive, aerospace and other fields that are very sensitive to environmental contamination.
It is important to monitor and maintain the cleanliness/contamination levels in the clean rooms. Further, for maintaining the cleanliness/contamination levels in the clean room, it is important to test/inspect a sample for cleanliness standard, before sending the sample to the clean room. Hence, cleanliness of a new sample coming to the clean room environment is very important.
In addition, in the mentioned industries it is customary to carry out preventive maintenance of manufacturing tools such as sputtering, CVD, etch, and other tools. As part of this procedure some of the parts require renovation and cleaning. Therefore, it is of high importance to be able to test cleanliness of the part before reinstalling it to a machine.
Conventionally, visual inspection techniques have been used with ultraviolet or oblique white light. Ultraviolet light is employed to take advantage of the fact that certain organic particles fluoresce. Alternatively, white light is shined towards a test surface at an angle so as to produce reflections that can be visualized. While the white light technique is slightly more sensitive than the ultraviolet technique, they both suffer from a common limitation. These visual inspection techniques only allow a cursory inspection of the sample or surface conditions. Further, the visual inspection techniques, at best, only detect particles that are larger than twenty microns. If, it is desirable or requirement to detect particles that are less than one micron, conventional techniques fails to achieve the goal. Furthermore, these conventional techniques are very tedious and time consuming.
Other conventional techniques include particle counters, which are intended for measuring particles on the surface. However, one of the main disadvantages of this technique is that it is localized and does not account for the complete sample.
Yet another conventional technique include Liquid Particle Counters, which are intended for measuring particles removed from a sample after flowing clean water through the sample. However in this case the sample cannot be further used and needs to be either dissected or processed (cleaned) again.
Hence, there is a need for apparatus and method that can determine cleanliness of a sample, before shipping or taking the sample to clean room environment. Further, there is a need for a method and apparatus that can determine the cleanliness of the sample in a convenient and effective manner.